Fig. 1
From: TGF-β in fibrosis by acting as a conductor for contractile properties of myofibroblasts
Actin-myosin crossbridge (CB) cycle [57]. Cycle of ATP-ADP-Pi actin-myosin interaction. The CB cycle is composed of six successive conformational steps, i.e. three detached steps (D1, D2, and D3) and three attached steps (A1, A2, and A3). Transition A3 → D1 is the ATP binding step that induces CB detachment after ATP binding to the actin (A)-myosin (M) complex (AM). The rate constant for detachment is g2: AM → A + M. Transition D1 → D2 is the ATP hydrolysis: M + ATP → M-ADP-Pi. Transition D2 → D3 is M-ADP-Pi → M*-ADP-Pi. D3 is the step with the highest probability. Transition D3 → A1is the attachment state: the myosin head (M*-ADP-Pi) binds to A and the rate constant for attachment is f1: M-ADP-Pi + A → AM-ADP-Pi. Transition A1 → A2 is the power stroke which is triggered by the Pi release: AM-ADP-Pi → AM-ADP + Pi. The power stroke is characterized by the generation of a unitary CB force (\(\cong\) picoN) and an elementary CB step (\(\cong\) nm). Transition A2 → A3 is the release of ADP: AM-ADP → AM + ADP